8.19 Automatic dependency tracking

As a developer it is often painful to continually update the
Makefile.am whenever the include-file dependencies change in a
project. Automake supplies a way to automatically track dependency
changes (see Dependency Tracking).

Automake always uses complete dependencies for a compilation,
including system headers. Automake’s model is that dependency
computation should be a side effect of the build. To this end,
dependencies are computed by running all compilations through a
special wrapper program called depcomp. depcomp
understands how to coax many different C and C++ compilers into
generating dependency information in the format it requires.
‘automake -a’ will install depcomp into your source
tree for you. If depcomp can’t figure out how to properly
invoke your compiler, dependency tracking will simply be disabled for
your build.

Experience with earlier versions of Automake (see Dependency Tracking Evolution in Brief History
of Automake) taught us that it is not reliable to generate dependencies
only on the maintainer’s system, as configurations vary too much. So
instead Automake implements dependency tracking at build time.

Automatic dependency tracking can be suppressed by putting
no-dependencies in the variable AUTOMAKE_OPTIONS, or
passing no-dependencies as an argument to AM_INIT_AUTOMAKE
(this should be the preferred way). Or, you can invoke automake
with the -i option. Dependency tracking is enabled by default.

The person building your package also can choose to disable dependency
tracking by configuring with --disable-dependency-tracking.